Mo元素对NiCrBSi合金激光熔覆层开裂敏感性的影响

Effect of molybdenum on crack sensibilities of laser cladded NiCrBSi alloy coatings

采用CO2固体激光器,在45CrNi钢表面制备了添加成分(质量分数,%)为0,2.5,5.0,7.5,10.0Mo的NiCrBSi合金熔覆层,研究了Mo元素对熔覆层开裂敏感性的影响,并从线膨胀系数和熔覆层凝固组织特性两方面对其影响进行了分析.结果表明,NiCrBSi合金对裂纹很敏感,熔覆层表面出现大量横向宏观裂纹,NiCrBSi合金中添加质量分数5.0%Mo,可改善凝固组织中硬质相的成分和形态,降低熔覆层的线膨胀系数,二者综合作用,降低了熔覆层的开裂敏感性.

Five kinds of coatings have been prepared on the surface of 45CrNi steel plates using laser cladded technique by adding 0,2.5 wt.%,5 wt.%,7.5 wt.% and 10 wt.% Mo into the NiCrBSi alloys.The effect of molybdenum on the crack sensibitities of laser cladded NiCrBSi alloy coatings of these five kinds of coatings were investigated by oil whiting test.Crack sensibitities are affected by the coefficient of thermal expansion of the coatings and the solidification characteristics and microstructures.The research results present that NiCrBSi alloy is very sensitive to cracking and many transverse macro cracks appear on the clad pass.While the sizes of dendrites and the carbides morphologies of eutectic microstructure of the coating with 5.0 wt.% of Mo are different frorn the others.Meanwhile,the coefficient of thermal expansion of the coating is decreased.Both of two effects are responsible for the reduction of crack sensibilities.